The invention relates to a rotary switch for a glass ceramic cooktop.
In household appliances, control elements which may be embodied as rotary switches, sliding switches or as electronic switches, touch-sensitive (contact) switches for example, are well-known for the purpose of activating or setting functions. The use of rotary switches is preferred owing to their good operability. In the case of household appliances which constitute a glass ceramic cooktop, which is also referred to as a glass ceramic stovetop, the use of rotary switches has, however, been possible only to a limited extent hitherto.
In DE 20 2005 019 978 U1, for example, a control device is described which can represent a rotary switch, for example. In this case, in one embodiment, one part of the rotary switch, which represents a rotary control, is provided on the top of the glass ceramic plate and interacts contactlessly with sensor elements which are disposed on the underside of the glass ceramic plate such that control signals are transmitted to a controller that is disposed underneath the plate. In a further embodiment, the rotary control disposed on the glass ceramic plate is connected via a control device axis or, as the case may be, rotational axis to a control device which represents an energy controller. In this arrangement the rotational axis projects through an opening in the plate. Also provided on the control device, in particular on the rotary control, are contact sensors via which further functions of the appliance actuated by means of the control device can be activated. For example, the contact sensors can be used for switching a hotplate on and off. In the embodiment in which the rotary control is connected to the control device via a rotational axis, the signals of the contact sensors are transmitted along the rotational axis.
A disadvantage of this known control device is that in the case of the embodiment in which no opening is provided, the signal for controlling the hotplate can only be transmitted by magnetic or optical means. As a result, a relatively complex and expensive design is required and the detection function can easily be affected by accumulated dirt or other external influences. Conversely, in the case of the embodiment in which the rotary position of the rotary knob is transmitted via a rotational axis, i.e. mechanically, the rotary position is available solely as an input for the control device. In the last-mentioned embodiment, therefore, the rotary position cannot be used for other purposes.